Researchers from the University of South Carolina and Rutgers University said they hacked two popular tire pressure monitoring systems; they'll report their findings at the USENIX Security conference in Washington, DC, this week.

Security features on tire pressure monitoring systems, a mandatory safety feature on all new vehicles, are limited--the main deterrent to hacking them is that their communications protocol isn't widely published. Using $1,500 in equipment, researchers were able to pick up a car's tire pressure readings and decipher the communication protocol by examining the radio transmission.

While tire pressure monitor hacks aren't particularly threatening to occupants, researchers say hackers could use the weakness to track a vehicle or possibly cause its electronic control unit, which controls the cars electronic stability control feature and tire pressure monitoring system, to malfunction or fail.

The researchers' finding highlights the need for manufacturers to add security precautions as more automakers add wireless communication technology to vehicles.